2016/01/31 by Ben David Normann, Ben Normann, Iver Brevik · 48 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #COSMIC cancer database #Cosmology and Gravitation Theories #Formalism (music) #Galaxies: Formation, Evolution, Phenomena #Limit (mathematics) #Magnitude (astronomy) #Quintessence #Viscosity #Viscous liquid #Volume viscosity #gr-qc
paper · pdf · doi:10.3390/e18060215
published in Entropy 18(6), 215 (Multidisciplinary Digital Publishing Institute) · 15 pages, one figure. Major revision of the manuscript; new title. Version to appear in Entropy
arxiv created 2016/05/27 · openalex publication_date 2016/06/02 · arxiv updated 2016/06/03 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We derive a general formalism for bulk viscous solutions of the energy-conservation equation for ρ ( a , ζ ) , both for a single-component and a multicomponent fluid in the Friedmann universe. For our purposes, these general solutions become valuable in estimating the order of magnitude of the phenomenological viscosity in the cosmic fluid at present. H ( z ) observations are found to put an upper limit on the magnitude of the modulus of the present-day bulk viscosity. It is found to be ζ 0 ∼ 10 6 Pa·s, in agreement with previous works. We point out that this magnitude is acceptable from a hydrodynamic point of view. Finally, we bring new insight by using our estimates of ζ to analyze the fate of the future universe. Of special interest is the case ζ ∝ ρ for which the fluid, originally situated in the quintessence region, may slide through the phantom barrier and inevitably be driven into a big rip. Typical rip times are found to be a few hundred Gy.